Each month, car and light truck manufacturers report the number of U.S.-produced cars and light trucks they sold in the U.S. the previous month. As with home sales, vehicle sales are an indication of the strength of consumer spending and optimism.
Based on the monthly numbers, seasonally adjusted annual sales rates are calculated, and those are the numbers market-watchers pay attention to. (Although some economists prefer to wait a day or so for the total number of cars and light trucks sold in the U.S. during the month, domestic and foreign, and compare the seasonally adjusted annual sales rate to the previous month.) Carmakers report their numbers over the course of a day or two, generally during the first week of the month, and the totals hit the wires once all the companies have reported.